It is the understanding of the Iowa Department of Public Health that residents located near the Pattison Sand Mine are concerned with the potential for adverse health impacts from fugitive dust originating from sand that is stored on the property and from any potential adverse health impacts from the acrylamide that is present in the flocculent used at the mine and that could be present in sand that is reused on or near the mine. This consultation will first include a discussion of potential nuisance issues from silica dust generated from the operation of the Pattison Sand Company. This consultation secondly will include a discussion of the potential for human exposure and the potential for adverse health impacts from the presence of acrylamide from that may be present in the flocculent.
Discussion – Health Impacts from Exposure to Silica Dust
It is well recognized that occupational exposures to respirable crystalline silica are associated with the development of silicosis, lung cancer, pulmonary tuberculosis, and airways diseases. Because of this the National Institute for Occupational Safety and Health (NIOSH), the Occupational Safety and Health Administration (OSHA), and the Mine Safety and Health Administration (MSHA) have all developed recommended and permissive exposure levels that are deemed to be safe for exposure to workers employed in industries that mine and utilized silica sand and can be exposed to very fine or respirable crystalline silica. Respirable crystalline silica is defined as that portion of airborne crystalline silica that is capable of entering the gas-exchange regions of the lungs if inhaled. This is generally determined to be a particle-size-selective fraction of the total airborne dust that includes particles with aerodynamic diameters less than approximately 10 microns or micrometers (μm). Particles that are 10 μm in size are about one-fifth of the diameter or a strand of human hair and are similar in size to pollen and mold spores. Table 1 includes a summary of the safe exposure levels from these agencies.
Table 1 – Source, Type, and Level of Safe Occupational Respirable Silica Exposure Levels
The most conservative safe occupational respirable silica exposure level is the level developed by NIOSH – a level of 0.05 mg/m3 or 50 micrograms per cubic meter (µg/m3). This is the level that I will be using as a level to compare to any air testing results. This level is based upon health and epidemiological studies that have completed on individuals who have been exposed to respirable silica levels over many years of working in that industry. One of these studies estimated 2 percent of workers exposed at 0.05 mg/m3 for 40 years developed silicosis. Another study estimated that a worker is exposed at 0.05 mg/m3 for 25 years had a 9 percent chance of developing silicosis. In an additional study an exposure level of 0.05 mg/m3 was estimated to cause an addition risk ranging from 0.4 percent to 0.9 percent after 40 years of exposure. After a review of these occupational health studies and considering that these occupational studies observed health impacts after 25 to 40 years of exposure, I conclude that an exposure to respirable silica at or below a level of 0.05 mg/m3 or below would not cause adverse health impacts to residents living in the area of the Pattison Mining Company’s operation and exposed to respirable silica on a periodic basis.
The Pattison Sand Company provided some recent monitoring results for respirable dust and crystalline silica at the mine location, in Clayton located to the north, and in Guttenberg located to the south. The monitoring results along with several maps showing the monitoring locations are attached to this letter. Table 2, identifies monitoring locations and monitoring results.
Table 2 – Monitoring Locations and Monitoring Results for Respirable Dust and Crystalline Silica
According to conversations with Pattison Sand Company officials, this monitoring event was conducted on April 22, 2016 and was during normal operations and several days after rains occurred at the site.
The results of the monitoring completed by the Pattison Sand Company communicate two concentrations. One of the concentrations is for respirable dust and the other concentration is for respirable crystalline or quartz silica. Both of these levels represent particles that are 10 microns in size and smaller. The level for dust represents all particles within the sample of air that was below 10 microns in size and the level for crystalline represents crystalline or quartz particles within the sample of air that was below 10 microns in size.
The highest level of respirable crystalline particles during the April 22, 2016 monitoring event was
0.019 mg/m3 at the sampling location in Clayton, Iowa. This level is below the NIOSH recommended exposure level of 0.050 mg/m3 and would be considered to not cause adverse health impacts to people exposed at this level.
The highest level of respirable dust during the April 22, 2016 monitoring event was 0.061 mg/m3 at center and the west end of the mine. The interpretation of this leve means that due to the uncertainty of the laboratory detection method, the level of respirable dust could not be accurately determine but was at some level below 0.061 mg/m3. The level can be compared to the U.S. Environmental Protection Agency (EPA) National Ambient Air Quality Standard (NAAQS) for particle matter below 10 microns
(PM10). The NAAQS for PM10 is 0.150 mg/m3. The NAAQS for PM10 is a level that is intended to provide public health protection, including protecting the health of "sensitive" populations such as asthmatics, children, and the elderly. The level highest level for respirable dust is below the EPA NAAQS for PM10 and would be considered to not cause adverse health impacts to people exposed at this level.Discussion – Exposure to Acrylamide in Sand
Some residents in the vicinity of the Pattison Sand Company mine have expressed concern regarding one of the chemicals that could be present in the flocculent used in the mining operations and could be present within the sand and have potential for adverse health impacts to people living near the mine.
The chemical is acrylamide. Attached to this letter is health and environmental safety information on the anionic polyacrylamide that is use as a flocculent. The actual flocculent is essentially non-toxic since the size of the molecules are too large to be absorbed into cells with the body. But since acrylamide is used in the manufacture of the compound, the potential for exposure to acrylamide can be a concern.
Exposure to large amounts of acrylamide can cause nervous system effects such as muscle weakness, numbness in hands and feet, sweating, unsteadiness, and clumsiness. The EPA, International Agency for Research on Cancer (IARC), National Toxicology Program (NTP), and the Department of Health and Human Services has concluded that acrylamide is likely to be carcinogenic to humans. Direct exposure to sand or surface or groundwater containing sufficient quantities of acrylamide would be necessary for a person to have a potential of experiencing any of the adverse health effects discussed above. Sampling of either the sand or surface water runoff from the sand piles for acrylamide can be utilized in order to determine the potential of adverse health impacts from acrylamide exposure.
Laboratory methods for sampling and analyzing sand for acrylamide have not been established, but there is a laboratory method that can be used for analyzing water for acrylamide. The Pattison Sand Company provided several analyses of surface water for acrylamide at the mine site. Copies of these analytical reports are attached to this letter. Table 3 includes a summary of levels of acrylamide found in these surface water samples.
Table 3 – Surface Water Sampling for Acrylamide
In all of the surface water samples the amount of acrylamide was below the laboratory detection method. In the surface water samples collected on April 20, 2016 the amount of acrylamide was below 0.005 mg/L. Although a regulatory maximum contaminant level for acrylamide has not been established, the EPA has developed health advisory levels for acrylamide in water. These levels have been established by looking at toxicological studies and can be use as safe levels of ingestion exposure to chemicals. A
1-day health advisory level of 1.5 mg/L and a 10-day health advisory level of 0.3 mg/L have been developed as safe levels of ingestion exposure to children for the specified time frame of exposure. In addition, the EPA has developed a drinking water equivalent level (DWEL) for acrylamide of 0.07 mg/L. According to EPA as DWEL is “a drinking water lifetime exposure level, assuming 100% exposure from that medium, at which adverse, non-carcinogenic health effects would not be expected to occur.”
Reviewing the results of the surface water sampling completed at the Pattison Sand Company mine site indicate that concentration of acrylamide found in surface water coming in contact with the piles of sand at the site is less than 0.005 mg/L. This concentration is less than the health advisory levels for acrylamide which would indicate that a person with direct ingestion exposure to the surface water would not experience adverse health impacts from acrylamide. The concentration of acrylamide in site groundwater would most likely be below and level of acrylamide in surface water. Therefore the levels of acrylamide within site groundwater and in groundwater near the site would also be below levels that would adversely impact human health.
Conclusions and Recommendations
This health consultation has evaluated the potential for adverse health impacts from exposure to respirable dust and silica and from acrylamide that may be present in the flocculent used in the processes on site. If the amount of airborne dust and silica remain close to the levels during the April 2016 sampling event it can be concluded that adverse respiratory health impact will not be experienced by workers at the mine site and by people living near the mine from inhalation exposure to dust and silica. It is recommended that periodic monitoring of respirable dust and silica be completed to ensure these levels remain below levels that can impact human health. It is also recommended that steps to taken to control the potential from fugitive dust through appropriate dust suppression measures.
In addition, the levels of acrylamide found within surface water runoff during the September 2013and April 2016 monitoring events at the site are below detectable laboratory methods and below levels of acrylamide that would pose health impacts to people using this surface water as drinking water. It is recommended that sampling and analysis of surface water runoff at the site for acrylamide be continued to ensure the levels of acrylamide in surface water at the site remain below levels that could adversely impact human health.
Air Sampling locations